The present invention is directed to a particle filtration, oil de-emulsifying, oil coalescing and oil collecting system. More particularly, the present invention is directed to a particle filtration, oil de-emulsifying, oil coalescing and oil collecting system that uses a needle punch polymer primary filter and a microfiber polymer secondary filter in a coiled tubular arrangement.
Devices, systems and methods for the removal of particles, free oil (such as dispersed, finely divided oil droplets), and emulsified oil contaminants in aqueous fluids is in widespread use in all types of commercial and industrial facilities. Known devices include cartridge and bag filters either permanently installed or as a part of portable systems, conventional oil coalescing systems that require many stages, baffles, filters, and weirs to coalesce and then separate and accumulate the coalesced oil, membrane filtration systems that concentrate emulsified oils and particles in an aqueous fluid for disposal, and conventional oil skimmers that remove oils in aqueous fluid sumps or baths after the oil droplets begin to coalesce due to time and gravity. Known methods include periodically pumping out the old fluid and pumping in new coolant.
However, each of these known systems has its drawbacks. For example, cartridge and bag filters are subject to blinding by oil emulsions and contaminants and require high pressure pumps and housings. Oil coalescing systems are relatively expensive and difficult to clean and usually require a relatively large dedicated floor space, and do not remove emulsified tramp oils.
Membrane filters are unreliable due to their sensitivity to fouling by various contaminants and damage by pH and temperature. Membrane filters remove coalesced oils by holding back the oil and allowing aqueous fluids to pass through the filter. This concentrates the emulsion on one side of the membrane. As the concentration of oil increases, the efficiency of the filtration system decreases (due to increased resistance across the membrane) and the membrane becomes increasingly susceptible to fouling.
Periodic change-out of the coolant results in labor time and costs, machine down-time, coolant costs and disposal costs. Moreover, once the coolant is changed, it begins accumulating unwanted contaminants such that the quality of the coolant continually degrades until the next change-out.
Various attempts have been made to reduce fouling in membrane filters. These include using spinning discs near the surface of the membrane; however, these disks require relatively large amounts of energy and generate heat in the fluid. Moreover, membrane pore sizes are such that bacteria concentrates with the emulsion. The heat generated from the antifouling mechanisms tends to colonize bacteria and create offensive odors. Further, membrane filtration systems cannot be used to filter emulsified oil coolants for reuse because the membrane blinds (clogs or fouls) when it is used to filter out finely divided oil-in-water emulsions.
With respect to oil-in-water emulsions, these are liquid systems that are particularly difficult to filter. Such liquid systems include, for example, coolant systems having a (desired) oil droplet xe2x80x9csurroundedxe2x80x9d by coolant. That is, the oil-in-water forms a micelle-like liquid system with a desirable oil in the nucleus of the micelle and the coolant surrounding the oil nucleus. The xe2x80x9cdesirablexe2x80x9d oil may be, for example, a particular lubricating oil. In such systems, tramp oils such as (other, undesirable) lubricating oils, hydraulic fluids and part coating oils (collectively contaminants) maybe present in the coolant system. These contaminants adhere or attach to the outer liquid of the system. It is these contaminants that must be removed, without removing the desirable oils.
Oil skimmers are essentially a remediation strategy to remove unwanted oils after they have become a problem. Floating oils typically prevent the movement of oxygen and create an environment for the cultivation of anaerobic bacteria. Floating oils can also form dry floating patches of material that are not effectively picked up by conventional skimming techniques. However, oil skimmers do not remove emulsified tramp oils. The emulsified oils can also become food to cultivate bacteria as well as change the cooling and machining enhancement properties of the coolant.
Accordingly, there is a need for a filter system that is less susceptible to fouling and that can remove unwanted contaminants. Desirably, such a filter system is configured to allow contaminants to first pass over a used area of the filter prior to exposing the contaminants to unexposed areas of the filter. Most desirably, such a filter system increases the ability of oil and particulate contaminants to be removed without prematurely blinding the filter media. Such a system most desirably operates at low pressure differentials to promote high efficiency and to eliminate the need for high pressure pumps and additional structural elements to support these higher operating pressures.
A filter system for receiving an oil-in-water emulsion contaminated with an emulsified contaminant oil, and separating the emulsified contaminant oil from the oil-in-water emulsion includes a filter media for receiving the oil-in-water emulsion and emulsified contaminant oil. The filter media has an inner filter element formed from a 5 micron nominal, 48 micron 95 percent efficiency single pass filtering material of needle punch polypropylene felt, an outer filter element formed from a 19 micron 95 percent efficiency single pass filtering material of a polypropylene microfiber material and a porous spunbond polypropylene surrounding the outer filter media.
The filter element de-emulsifies the emulsified contaminant oil from the oil-in-water emulsion into the contaminant oil and the oil-in-water emulsion, coalesces the de-emulsified contaminant oil, separates the coalesced de-emulsified contaminant oil from the oil-in-water emulsion, and passes both the coalesced de-emulsified contaminant oil and the oil-in-water emulsion.
A first tank supports the filter element, The first tank is further configured to hold a quantity of the coalesced de-emulsified contaminant oil and the oil-in-water emulsion. The first tank includes an overflow passing to a second tank.
The second tank has an oil separation assembly for removing the oil-in-water emulsion from the contaminant oil and passing the oil-in-water emulsion therefrom. In a present system, the oil separation assembly includes a vertical conduit extending to about a bottom of the tank and a tee in flow communication with the vertical conduit. The tee provides flow communication from the second tank such that the oil-in-water emulsion flows upward into the vertical conduit, into the tee and out of the second tank. The lighter coalesced oil, however, floats on top of the oil-in-water emulsion in the second tank and is precluded from exiting the second tank until the oil depth exceeds the depth of the vertical conduit.
Preferably, the oil-in-water emulsion is recovered and reused. The contaminant oil is also recovered for subsequent treatment and/or disposal.
The filter system can include an over-pressurization arrangement to prevent over-pressurizing the filter media.
In a present filter system, an optional pre-separation system is disposed prior to the first tank. The pre-separation system separates contaminant oil (e.g., tramp oils xe2x80x9cfloatingxe2x80x9d on the surface) from the oil-in-water emulsion that is contaminated with the emulsified contaminant oil. A present separation system is a belt skimmer.
A method for separating an oil-in-water emulsion from a liquid system having an oil-in-water emulsion contaminated with an emulsified contaminant oil includes the steps of introducing the oil-in-water emulsion contaminated with the emulsified contaminant oil through a filter media to form an oil-in-water emulsion and a separated contaminant oil stream, passing the oil-in-water emulsion through the filter media, passing the contaminant oil through the filter media, separating the oil-in-water emulsion from the contaminant oil and recovering the oil-in-water emulsion.
The present systems use the natural ability of the coiled tubular filter configuration to de-emulsify and coalesce oils and makes use of gravity to facilitate separating and accumulating the coalesced oils, in a container, for ease of removal. A present system can be provided in a modular design having a relatively small footprint, which provides a cost effective, machine-dedicated system for example, for parts cleaners, machine tools and the like. Moreover, the present coalescing/de-emulsifying coiled tubular filter system is less susceptible to fouling and bacteria colonization than membrane filters because the coalesced oil, aqueous fluid, and any bacteria pass through the filter.
These and other features and advantages of the present invention will be apparent from the following detailed description, in conjunction with the appended claims.